• Energy Research

Distributed maximum power point tracking photovoltaic (PV) systems based on series-connected dc/dc converters are one of the most promising PV configurations for an enhanced security and efficiency in distributed generation systems. Most of the works reported so far in the literature for control and stability analysis of these configurations are based on small-signal ac models. This could be a significant limitation, as this kind of linearization produces a good approximation of the nonlinear model of series-connected dc/dc converters only at the operating point. However, PV systems must be controlled for a large set of operating points with a satisfactory performance and robustness. Moreover, stability analysis of series-connected dc/dc converters has not yet been widely discussed in previous research. Therefore, this article presents a nonlinear model of series-connected boost dc/dc converters and develops control and stability analysis to fill the gap in this emerging topic. A systematic experimental and numerical investigation is performed in order to validate the effectiveness of the proposed control approach in this study.

This paper proposes a fault identification system for short and open-circuit switch faults (SOCSF) for a dc/dc converter acting as a Maximum Power Point Tracker (MPPT) in Photovoltaic (PV) systems. A closed-loop operation is assumed for the boost dc/dc converter. A linearizing control plus a Proportional-Derivative (PD) controller is suggested for PV voltage regulation at the maximum power point (MPP). In this study, the SOCSF are modeled by using an additive fault representation and the fault identification (FI) system is synthesized departing from a Luenberger observer. Hence, an FI signal is obtained, which is insensitive to irradiance and load current changes, but affected by the SOCSF. For FI purposes, only the sensors used in the control system are needed. Finally, an experimental evaluation is presented by using a solar array simulator dc power supply and a boost dc/dc converter of 175 W in order to validate the ideas this study exposes.